A high-efficiency, high-temperature acid leaching process for refining high-purity quartz sand

Abstract

The present invention belongs to the technical field of quartz sand purification, and discloses a high-efficiency, high-temperature acid leaching process for refining high-purity quartz sand. The process of the present invention comprises the following steps: mixing quartz sand raw material with a first acid solution, performing pre-acid leaching, and obtaining pretreated quartz sand; using a second acid solution to sequentially perform a first acid leaching treatment and water quenching on the pretreated quartz sand to obtain primary treated quartz sand; using a third acid solution to perform a second acid leaching treatment on the primary treated quartz sand to obtain high-purity quartz sand. The present invention uses industrially difficult-to-process fluorine-containing waste sulfuric acid as a pickling liquid, combined with a high-temperature pickling process, which can not only effectively react with impurities in the quartz sand, ensuring that the quartz sand crystals are not damaged and realizing the bulk consumption of fluorine-containing waste sulfuric acid, but also greatly shorten the time of the acid leaching treatment, which is beneficial to cost reduction and efficiency improvement in the quartz sand refining industry, while eliminating the generation of Cl-containing wastewater, meeting environmentally friendly requirements, and being suitable for large-scale industrial production.

Description

Technical Field

[0001] The invention relates to the technical field of quartz sand purification, and in particular to a high-efficiency high-temperature acid leaching process for refining high-purity quartz sand. Background Art

[0002] Fluorine-containing waste sulfuric acid, due to its strong acidity and corrosive properties, can severely corrode treatment equipment. Furthermore, the technical difficulty of effectively separating fluoride ions from other useful components in waste sulfuric acid makes its harmless treatment and resource utilization a major challenge. Currently, treating this type of fluorine-containing waste sulfuric acid often requires the combined application of multiple processes, but the complexity of synergy and integration between these processes makes it difficult to achieve ideal treatment results. Therefore, the search for efficient and cost-effective treatment solutions for fluorine-containing waste sulfuric acid is particularly urgent.

[0003] Quartz sand is currently widely used in the construction industry, particularly in the production of high-end building and decorative materials. High-whiteness quartz sand can significantly enhance the aesthetic value and texture of the product. However, crude quartz sand often contains impurities such as iron, resulting in insufficient whiteness, which negatively impacts the overall visual quality of the building material. Furthermore, improper pickling or impurity removal during processing can further reduce the whiteness of the quartz sand and even cause noticeable color differences. Therefore, refining crude quartz sand is particularly important.

[0004] In the field of quartz sand refining, pickling process is an important means to improve product quality. Quartz sand refining pickling process mainly includes: single pickling agent pickling process (hydrochloric acid, sulfuric acid or hydrofluoric acid, etc.), mixed pickling agent pickling process (mixed hydrochloric acid and sulfuric acid, mixed hydrofluoric acid and oxalic acid), pickling combined with other processes (pickling-magnetic separation combined process, pickling-flotation combined process), etc. Traditionally, single pickling agent has been difficult to meet the increasingly stringent refining requirements due to its limited effect. Although mixed pickling agents can significantly improve the pickling effect, the high cost limits its widespread application. In addition, considering the strict restrictions of environmental protection policies on the discharge of chloride ion wastewater, many regions have banned the direct discharge of such wastewater, which undoubtedly further increases the difficulty of treatment. Summary of the Invention

[0005] The purpose of the present invention is to provide a high-efficiency and high-temperature acid leaching process for refining high-purity quartz sand, so as to solve the problem that fluorine-containing waste sulfuric acid cannot be processed in bulk and the quartz sand pickling process has many limitations.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a high-efficiency high-temperature acid leaching process for refining high-purity quartz sand, comprising the following steps:

[0008] (1) mixing the quartz sand raw material with the first acid solution and performing pre-acid leaching to obtain pretreated quartz sand;

[0009] (2) using a second acid solution to sequentially perform a first acid leaching treatment and a water quenching on the pretreated quartz sand to obtain a primary treated quartz sand;

[0010] (3) The first-treated quartz sand is subjected to a second acid leaching treatment using a third acid solution to obtain high-purity quartz sand.

[0011] Preferably, in the high-efficiency high-temperature acid leaching process for refining high-purity quartz sand, in step (1), the first acid solution comprises, by mass, 30 to 40 parts of fluorine-containing waste sulfuric acid, 0.5 to 2 parts of hydrogen peroxide, and 60 to 70 parts of water.

[0012] Preferably, in the high-efficiency high-temperature acid leaching process for refining high-purity quartz sand, in step (1), the solid-liquid ratio of the pre-acid leaching is 0.5 to 3:1, the temperature of the pre-acid leaching is 20 to 40°C, and the time of the pre-acid leaching is 3 to 6 hours.

[0013] Preferably, in the high-efficiency high-temperature acid leaching process for refining high-purity quartz sand, in step (2), the second acid solution comprises, by mass, 25 to 40 parts of fluorine-containing waste sulfuric acid, 1 to 5 parts of a reducing agent, and 60 to 70 parts of water.

[0014] Preferably, in the high-efficiency high-temperature acid leaching process for refining high-purity quartz sand, in step (2), the solid-liquid ratio of the first acid leaching treatment is 0.2 to 2:1, the temperature of the first acid leaching treatment is 80 to 100°C, and the time of the first acid leaching treatment is 1 to 3 hours.

[0015] Preferably, in the high-efficiency high-temperature acid leaching process for refining high-purity quartz sand, in step (2), the temperature of the water used for the water quenching is 1 to 10°C.

[0016] Preferably, in the high-efficiency high-temperature acid leaching process for refining high-purity quartz sand, in step (3), the third acid solution comprises, by mass, 30 to 40 parts of fluorine-containing waste sulfuric acid, 2 to 10 parts of a chelating agent, and 55 to 65 parts of water.

[0017] Preferably, in the high-efficiency high-temperature acid leaching process for refining high-purity quartz sand, the reducing agent is thiourea dioxide;

[0018] The chelating agents include sodium citrate or sodium ascorbate.

[0019] Preferably, in the high-efficiency high-temperature acid leaching process for refining high-purity quartz sand, in step (3), the solid-liquid ratio of the second acid leaching treatment is 0.2 to 2:1, the temperature of the second acid leaching treatment is 80 to 100°C, and the time of the second acid leaching treatment is 1 to 3 hours.

[0020] Preferably, in the high-efficiency high-temperature acid leaching process for refining high-purity quartz sand, the fluorine-containing waste sulfuric acid in the first acid solution of step (1), the second acid solution of step (2), and the third acid solution of step (3) independently include the following components in mass fraction: HF: 2-6%, H2SO4: 75-85%, and H2O: 14-18%.

[0021] It can be seen from the above technical solutions that compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) In the process of the present invention, pre-acid leaching can preliminarily reduce the impurity metal content of quartz sand, and help to improve the wettability of quartz sand in low-concentration hydrofluoric acid during the pickling process, open the lattice system of quartz sand, and expand the lattice cracks of quartz sand in the microscopic state, which is conducive to the further penetration of hydrofluoric acid solution into the interior of the quartz lattice system in the subsequent two-step high-temperature acid leaching process, dissolving the internal impurities, improving the cleaning effect of high-temperature pickling quartz sand, and improving the efficiency of high-temperature pickling.

[0023] (2) The process of the present invention includes a two-step high-temperature acid leaching process, which can make the quartz sand fluffy, expand the lattice system, and further increase the cracks in the quartz sand. At the same time, under the conditions of high-temperature acid leaching, sulfuric acid changes from a low-energy state to a high-energy state, which can effectively penetrate into the pores and cracks of the quartz sand, and react violently with trace impurity elements such as Al, Ca, Cu, Fe, Mn, etc. contained in the quartz sand to form soluble salts or complexes, washing and purifying the quartz sand, thereby removing the impurity elements contained in the solid quartz sand inclusions. In addition, the two-step acid leaching process is set to high-temperature acid leaching (80-100°C). High-temperature acid leaching is conducive to enhancing the molecular motion between the acid solution and the quartz sand, so that the acid solution can penetrate into the interior of the quartz sand particles faster, fully contact with the impurity elements and react. Compared with room-temperature acid leaching, the pickling efficiency of high-temperature acid leaching can be increased by more than 50%, greatly shortening the acid leaching treatment time. In addition, since the fluorine-containing waste sulfuric acid is diluted, the high-temperature acid leaching treatment at low fluorine concentration can also maintain the integrity of the quartz sand crystals and avoid excessive corrosion or damage.

[0024] (3) Low-temperature water quenching is performed directly after the first acid leaching treatment. This not only further increases the microcracks generated in the quartz sand, providing favorable conditions for the subsequent second-step high-temperature acid leaching and accelerating the treatment efficiency of the second-step high-temperature acid leaching; in addition, the physical scouring during the water quenching process also helps to remove residual impurities and reaction products attached to the surface of the quartz sand, thereby further improving the efficiency of the second-step high-temperature acid leaching treatment.

[0025] (4) Thiourea dioxide is added to the first step of high-temperature acid leaching. As a reducing agent instead of sodium dithionite, it can synergistically improve the impurity removal effect with the acidic components in the acid solution. In an acidic environment, thiourea dioxide can release reducing sulfide ions or sulfite ions, which undergo redox reactions with iron ions, reducing them to a more soluble or easier to remove form. In the second step of high-temperature acid leaching, a chelating agent is added. The chelating agent can form a stable complex with metal ions, especially selectively combining with iron ions to form a hardly soluble or insoluble complex precipitate, further improving the iron removal efficiency of quartz sand and improving the whiteness and purity of quartz sand.

[0026] (5) The present invention uses industrially difficult-to-treat fluorine-containing waste sulfuric acid as the pickling liquid, combined with a high-temperature pickling process. This not only effectively reacts with impurities in quartz sand, protecting the quartz sand crystals from damage and achieving large-scale disposal of fluorine-containing waste sulfuric acid, but also significantly shortens the acid leaching process time, thereby benefiting the quartz sand refining industry in reducing costs and increasing efficiency, while also eliminating the generation of Cl-containing wastewater. The resulting acid leaching wastewater is easier to treat, meets environmentally friendly requirements, and is suitable for large-scale industrial production. DETAILED DESCRIPTION

[0027] The present invention provides a high-efficiency high-temperature acid leaching process for refining high-purity quartz sand, comprising the following steps:

[0028] (1) mixing the quartz sand raw material with the first acid solution and performing pre-acid leaching to obtain pretreated quartz sand;

[0029] (2) using a second acid solution to sequentially perform a first acid leaching treatment and a water quenching on the pretreated quartz sand to obtain a primary treated quartz sand;

[0030] (3) The first-treated quartz sand is subjected to a second acid leaching treatment using a third acid solution to obtain high-purity quartz sand.

[0031] In the present invention, in step (1), the mass fraction of fluorine-containing waste sulfuric acid in the first acid solution is preferably 30 to 40 parts, more preferably 32 to 38 parts, and even more preferably 38 parts.

[0032] In the present invention, in step (1), the mass fraction of hydrogen peroxide in the first acid solution is preferably 0.5 to 2 parts, more preferably 1.5 to 2 parts, and more preferably 1.5 parts.

[0033] In the present invention, in step (1), the mass fraction of water in the first acid solution is preferably 60 to 70 parts, more preferably 60.5 to 66 parts, and more preferably 60.5 parts.

[0034] In the present invention, in step (1), the solid-liquid ratio of the pre-acid leaching is preferably 0.5 to 3:1, more preferably 1.5 to 3:1, and more preferably 2:1; the temperature of the pre-acid leaching is preferably 20 to 40°C, more preferably 25 to 30°C, and more preferably 25°C; the time of the pre-acid leaching is preferably 3 to 6 hours, more preferably 4 to 6 hours, and more preferably 5 hours.

[0035] In the present invention, during the pre-acid leaching process in step (1), the first acid solution is circulated by a circulation pump so that the first acid solution is in a flowing state.

[0036] In the present invention, in step (1), after the pre-acid leaching, the process preferably further comprises: washing until the washing waste liquid becomes neutral.

[0037] In the present invention, in step (2), the mass fraction of fluorine-containing waste sulfuric acid in the second acid solution is preferably 25 to 40 parts, more preferably 30 to 40 parts, and even more preferably 36 parts.

[0038] In the present invention, in step (2), the weight percentage of the reducing agent in the second acid solution is preferably 1 to 5 parts, more preferably 3 to 5 parts, and even more preferably 4 parts.

[0039] In the present invention, in step (2), the mass fraction of water in the second acid solution is preferably 60 to 70 parts, more preferably 60 to 67 parts, and even more preferably 60 parts.

[0040] In the present invention, the reducing agent is preferably thiourea dioxide.

[0041] In the present invention, in step (2), the solid-liquid ratio of the first acid leaching treatment is preferably 0.2 to 2:1, more preferably 1 to 2:1, and more preferably 2:1; the temperature of the first acid leaching treatment is preferably 80 to 100°C, more preferably 90 to 100°C, and more preferably 90°C; the time of the first acid leaching treatment is preferably 1 to 3 hours, more preferably 2 to 3 hours, and more preferably 3 hours.

[0042] In the present invention, during the first acid leaching treatment in step (2), the second acid solution is circulated by a circulation pump so that the second acid solution is in a flowing state.

[0043] In the present invention, in step (2), the temperature of the water used for the water quenching is preferably 1 to 10°C, more preferably 1 to 6°C, and even more preferably 2°C.

[0044] In the present invention, in step (2), water quenching is performed immediately after the first acid leaching treatment.

[0045] In the present invention, in step (3), the mass fraction of fluorine-containing waste sulfuric acid in the third acid solution is preferably 30 to 40 parts, more preferably 33 to 36 parts, and even more preferably 36 parts.

[0046] In the present invention, in step (3), the weight percentage of the chelating agent in the third acid solution is preferably 2 to 10 parts, more preferably 4 to 10 parts, and even more preferably 8 parts.

[0047] In the present invention, in step (3), the mass fraction of water in the third acid solution is preferably 55 to 65 parts, more preferably 56 to 60 parts, and even more preferably 60 parts.

[0048] In the present invention, the chelating agent preferably includes sodium citrate or sodium ascorbate, and more preferably includes sodium citrate.

[0049] In the present invention, in step (3), the solid-liquid ratio of the second acid leaching treatment is preferably 0.2 to 2:1, more preferably 1 to 2:1, and more preferably 2:1; the temperature of the second acid leaching treatment is preferably 80 to 100°C, more preferably 90 to 100°C, and more preferably 90°C; the time of the second acid leaching treatment is preferably 1 to 3 hours, more preferably 2 to 3 hours, and more preferably 3 hours.

[0050] In the present invention, during the second acid leaching treatment in step (3), the third acid solution is circulated by a circulation pump so that the third acid solution is in a flowing state.

[0051] In the present invention, in step (3), after the second acid leaching treatment, the following steps are preferably performed: washing until the washing waste liquid becomes neutral, drying, and screening.

[0052] In the present invention, the drying temperature is preferably 20 to 50°C, more preferably 25 to 40°C, and even more preferably 35°C.

[0053] In the present invention, there is no limitation on the screening process, and screening can be performed according to the required mesh size.

[0054] In the present invention, the mass fraction of HF in the fluorine-containing waste sulfuric acid in the first acid solution in step (1), the second acid solution in step (2), and the third acid solution in step (3) is independently preferably 2-6%, more preferably 4-6%, and more preferably 6%.

[0055] In the present invention, the mass fraction of H2SO4 in the fluorine-containing waste sulfuric acid of the first acid solution in step (1), the second acid solution in step (2) and the third acid solution in step (3) is independently preferably 75-85%, more preferably 78-82%, and more preferably 80%.

[0056] In the present invention, the mass fraction of H2O in the fluorine-containing waste sulfuric acid in the first acid solution of step (1), the second acid solution of step (2) and the third acid solution of step (3) is independently preferably 14-18%, more preferably 14-16%, and more preferably 14%.

[0057] In the present invention, there is no limitation on the preparation methods of the first acid solution in step (1), the second acid solution in step (2), and the third acid solution in step (3), and they can be mixed evenly.

[0058] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0059] Example 1

[0060] The fluorine-containing waste sulfuric acid used in Example 1 includes the following components by mass fraction: HF: 6%, H2SO4: 80%, H2O: 14%;

[0061] This embodiment provides a high-efficiency, high-temperature acid leaching process for refining high-purity quartz sand, comprising the following steps:

[0062] (1) 38 parts of fluorine-containing waste sulfuric acid, 1.5 parts of hydrogen peroxide, and 60.5 parts of water were mixed uniformly to prepare a first acid solution; quartz sand raw material (iron content 452 ppm) was immersed in the first acid solution with a solid-liquid ratio of 2:1, and the first acid solution was always kept in a flowing state by a circulating pump, and was immersed at 25°C for 5 hours, and then washed to neutrality to obtain pretreated quartz sand;

[0063] (2) By weight, 36 parts of fluorine-containing waste sulfuric acid, 4 parts of thiourea dioxide, and 60 parts of water were mixed evenly to prepare a second acid solution; the pretreated quartz sand was immersed in the second acid solution at a solid-liquid ratio of 2:1, and the second acid solution was kept in a flowing state by a circulating pump, and was immersed at 90°C for 3 hours; then, the pretreated quartz sand was immediately quenched with water at 2°C to obtain a first-treated quartz sand;

[0064] (3) By weight, 36 parts of fluorine-containing waste sulfuric acid, 8 parts of sodium citrate, and 60 parts of water were mixed evenly to prepare a third acid solution; the once-treated quartz sand was immersed in the third acid solution with a solid-liquid ratio of 2:1, and the third acid solution was always kept in a flowing state by a circulating pump, and was soaked at 90°C for 3 hours; then washed to neutrality, dried at 35°C, and sieved to obtain high-purity quartz sand of four specifications: >20 mesh, 20-40 mesh, 40-70 mesh, and 70-120 mesh.

[0065] Example 2

[0066] The fluorine-containing waste sulfuric acid used in Example 2 includes the following components by mass fraction: HF: 2%, H2SO4: 80%, H2O: 18%;

[0067] This embodiment provides a high-efficiency, high-temperature acid leaching process for refining high-purity quartz sand, comprising the following steps:

[0068] (1) 32 parts of fluorine-containing waste sulfuric acid, 2 parts of hydrogen peroxide, and 66 parts of water were mixed uniformly by weight to prepare a first acid solution; quartz sand raw material (iron content 452 ppm) was immersed in the first acid solution with a solid-liquid ratio of 1.5:1, and the first acid solution was always kept in a flowing state by a circulating pump, and was immersed at 40°C for 4 hours, and then washed to neutrality to obtain pretreated quartz sand;

[0069] (2) 30 parts of fluorine-containing waste sulfuric acid, 3 parts of thiourea dioxide, and 67 parts of water were mixed uniformly by weight to prepare a second acid solution; the pretreated quartz sand was immersed in the second acid solution at a solid-liquid ratio of 1:1, and the second acid solution was kept in a flowing state by a circulating pump, and was immersed at 100°C for 2 hours; then, the pretreated quartz sand was immediately quenched with water at 10°C to obtain a first-treated quartz sand;

[0070] (3) Calculated by weight, 40 parts of fluorine-containing waste sulfuric acid, 4 parts of sodium ascorbate, and 56 parts of water were mixed evenly to prepare a third acid solution; the once-treated quartz sand was immersed in the third acid solution with a solid-liquid ratio of 1:1, and the third acid solution was always kept in a flowing state by a circulating pump, and was soaked at 100°C for 2 hours; then washed to neutrality, dried at 25°C, and sieved to obtain high-purity quartz sand of four specifications: >20 mesh, 20-40 mesh, 40-70 mesh, and 70-120 mesh.

[0071] Example 3

[0072] The fluorine-containing waste sulfuric acid used in Example 3 includes the following components by mass fraction: HF: 4%, H2SO4: 80%, H2O: 16%;

[0073] This embodiment provides a high-efficiency, high-temperature acid leaching process for refining high-purity quartz sand, comprising the following steps:

[0074] (1) 35 parts of fluorine-containing waste sulfuric acid, 0.5 parts of hydrogen peroxide, and 64.5 parts of water were mixed uniformly by weight to prepare a first acid solution; quartz sand raw material (iron content 452 ppm) was immersed in the first acid solution with a solid-liquid ratio of 3:1, and the first acid solution was always kept in a flowing state by a circulating pump, and was immersed at 30°C for 6 hours, and then washed to neutrality to obtain pretreated quartz sand;

[0075] (2) By weight, 40 parts of fluorine-containing waste sulfuric acid, 1 part of thiourea dioxide, and 60 parts of water were mixed evenly to prepare a second acid solution; the pretreated quartz sand was immersed in the second acid solution at a solid-liquid ratio of 0.5:1, and the second acid solution was kept in a flowing state by a circulating pump, and was immersed at 80°C for 1.5 hours; then, the pretreated quartz sand was immediately quenched with water at 6°C to obtain a first-treated quartz sand;

[0076] (3) By weight, 33 parts of fluorine-containing waste sulfuric acid, 2 parts of sodium citrate, and 65 parts of water were mixed evenly to prepare a third acid solution; the once-treated quartz sand was immersed in the third acid solution with a solid-liquid ratio of 0.5:1, and the third acid solution was always kept in a flowing state by a circulating pump, and was soaked at 80°C for 1.5 hours; then washed to neutrality, dried at 40°C, and sieved to obtain high-purity quartz sand of four specifications: >20 mesh, 20-40 mesh, 40-70 mesh, and 70-120 mesh.

[0077] Comparative Example 1

[0078] This comparative example provides a treatment process for refining quartz sand. The difference from Example 1 is that the soaking temperature in step (2) is changed to 25°C and the soaking time is changed to 6 hours; the soaking temperature in step (3) is changed to 25°C and the soaking time is 6 hours. The other parameter conditions are the same as those in Example 1.

[0079] Comparative Example 2

[0080] This comparative example provides a treatment process for refining quartz sand. The difference from Example 1 is that water is deleted from the first acid solution, the second acid solution, and the third acid solution. Other parameter conditions are the same as those in Example 1.

[0081] Comparative Example 3

[0082] This comparative example provides a treatment process for refining quartz sand, which differs from Example 1 in that step (1) is deleted, and other parameter conditions are the same as those in Example 1.

[0083] Comparative Example 4

[0084] This comparative example provides a treatment process for refining quartz sand, which differs from Example 1 in that the second acid solution in step (2) is replaced by water, and other parameter conditions are the same as those in Example 1.

[0085] Comparative Example 5

[0086] This comparative example provides a treatment process for refining quartz sand, which differs from Example 1 in that the water quenching in step (2) is deleted, and other parameter conditions are the same as those in Example 1.

[0087] Comparative Example 6

[0088] This comparative example provides a treatment process for refining quartz sand, which differs from Example 1 in that thiourea dioxide in the second acid solution and the chelating agent in the third acid solution are deleted, and other parameter conditions are the same as those in Example 1.

[0089] The acid leaching treatment times of Examples 1 to 3 and Comparative Example 1 were compared, and the results are shown in Table 1.

[0090] Table 1. Comparison of two-step acid leaching treatment time of Examples 1 to 3 and Comparative Example 1

[0091]

[0092] The refined quartz sand products obtained in Examples 1 to 3 and Comparative Examples 1 to 6 were tested, and the test results are shown in Table 2.

[0093] Table 2. Test results of quartz sand products obtained in Examples 1 to 3 and Comparative Examples 1 to 6

[0094]

[0095]

[0096] The test results of Examples 1-3 and Comparative Example 1 show that compared to the high-temperature acid leaching in the examples, Comparative Example 1 uses room-temperature acid leaching to refine quartz sand. While maintaining the same purity, whiteness, and iron content, the high-temperature acid leaching in the examples significantly shortens the treatment time and significantly improves the treatment efficiency. This demonstrates that the high-temperature acid leaching process of the present invention offers excellent treatment effects and shortens the treatment time, making it more suitable for large-scale industrial production and beneficial for achieving cost reduction and efficiency improvement in the quartz sand pickling industry.

[0097] The test results of Example 1 and Comparative Example 2 show that in Comparative Example 2, undiluted fluorine-containing waste sulfuric acid is used to refine quartz sand. Although the differences in whiteness and iron content are not significant, hydrofluoric acid easily reacts with quartz sand at higher concentrations to form fluorosilicates, which erode the lattice of the quartz sand and cause the microscopic cracks in the quartz sand to "collapse", which is not conducive to the subsequent two-step high-temperature acid leaching treatment, resulting in a decrease in the purity of the quartz sand after pickling.

[0098] The test results of Example 1 and Comparative Example 3 show that the whiteness of the product of Comparative Example 3, which was not pre-acid leaching, is significantly reduced, and the iron content is also significantly increased. This shows that the solution without pre-acid leaching cannot open the lattice system of the quartz sand at the initial stage of treatment, and cannot enable the subsequent two-step high-temperature acid leaching process to further penetrate into the interior of the quartz lattice system for impurity removal, and the purity of the final quartz sand is also reduced.

[0099] The test results of Example 1 and Comparative Example 4 show that in Comparative Example 4, the acid solution in the first step of acid leaching treatment is replaced with water, which reduces the iron removal effect and the whiteness value also decreases.

[0100] The test results of Example 1 and Comparative Example 5 show that the water quenching process in step (2) is omitted in Comparative Example 5, and the iron removal effect and whiteness value are reduced, indicating that the water quenching process helps to improve the effect of the second step of high-temperature acid leaching treatment.

[0101] From the test results of Example 1 and Comparative Example 6, it can be seen that the reducing agent and the chelating agent are omitted in Comparative Example 6, and the iron removal effect and the whiteness value are reduced, indicating that the aforementioned additives can assist the acid solution in improving the impurity removal effect (especially iron removal) in an acidic environment.

[0102] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A high-efficiency, high-temperature acid leaching process for refining high-purity quartz sand, characterized in that: The following steps are involved: (1) mixing the quartz sand raw material with the first acid solution and performing pre-acid leaching to obtain pretreated quartz sand; (2) using a second acid solution to sequentially perform a first acid leaching treatment and a water quenching on the pretreated quartz sand to obtain a primary treated quartz sand; (3) performing a second acid leaching treatment on the once-treated quartz sand using a third acid solution to obtain high-purity quartz sand; In step (1), the first acid solution comprises, by weight, 30 to 40 parts of fluorine-containing waste sulfuric acid, 0.5 to 2 parts of hydrogen peroxide, and 60 to 70 parts of water; In step (2), the second acid solution comprises, by weight, 25 to 40 parts of fluorine-containing waste sulfuric acid, 1 to 5 parts of a reducing agent, and 60 to 70 parts of water; In step (3), the third acid solution comprises, by weight, 30 to 40 parts of fluorine-containing waste sulfuric acid, 2 to 10 parts of a chelating agent, and 55 to 65 parts of water; The fluorine-containing waste sulfuric acid in the first acid solution of step (1), the second acid solution of step (2), and the third acid solution of step (3) independently comprises the following components by mass: HF: 2-6%, H2SO4: 75-85%, and H2O: 14-18%; The reducing agent is thiourea dioxide; the chelating agent includes sodium citrate or sodium ascorbate; In step (1), the solid-liquid ratio of the pre-acid leaching is 0.5 to 3:1, the temperature of the pre-acid leaching is 20 to 40° C., and the time of the pre-acid leaching is 3 to 6 hours; In step (2), the solid-liquid ratio of the first acid leaching treatment is 0.2 to 2:1, the temperature of the first acid leaching treatment is 80 to 100° C., and the time of the first acid leaching treatment is 1 to 3 hours; In step (3), the solid-liquid ratio of the second acid leaching treatment is 0.2 to 2:1, the temperature of the second acid leaching treatment is 80 to 100° C., and the time of the second acid leaching treatment is 1 to 3 hours.

2. The high-efficiency high-temperature acid leaching process for refining high-purity quartz sand according to claim 1, characterized in that: In step (2), the temperature of the water used for the water quenching is 1 to 10°C.

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